The decoding in IRSA is an iterative process involving successive interference cancellation (SIC) [1]}, where the users are decoded via a combination of inter-RE and intra-RE SIC [2]}.
Inter-RE SIC refers to the removal of packet replicas from a different RE than the one the packet was decoded in, while intra-RE SIC refers to the removal of a packet from the same RE in which the packet was decoded, in order to facilitate decoding additional packets that may have been transmitted in that RE.
The conventional version of IRSA used only inter-RE SIC to decode users and assumed a collision model, wherein only singleton REs can be decoded [3]}.
Here, a singleton RE refers to an RE where a single user's packet is received without collision.
Since no packets can be decoded in REs where collisions occur, the maximum possible throughput is one packet per RE, the same as the throughput with perfectly coordinated multiple access.
This maximum can be achieved asymptotically as the number of users and REs go to infinity, when the soliton distribution is used to generate the repetition factors of the users [4]}.
